RF 2 Flashcards
AMPLITUDE of intelligence
Determines AMOUNT of carrier frequency deviation
FREQUENCY of intelligence
Determines RATE of carrier deviation
AMOUNT of carrier deviation
How FAR the carrier moves in frequency
RATE of carrier deviation
How FAST carrier moves in frequency
SCA
Subsidiary Communication Authorization
FM Stereo with SCA Decoding - FDM broadcast
- 0-15 kHz: BB L + R audio
- 19 kHz: Pilot carrier
- 23-37 + 39-53 kHz: L + R SBs
- 38 kHz: AMDSB-SC
- 57 kHz: Digital RBDS/RDS
- 59.5-75.5 kHz: SCA signal
- 67 kHz: SCA 1
- 92 kHz: SCA 2
AGC
Auto Gain Control
Frequency Hopping
Carrier signal switches in a pseudo-random fashion
Frequency Chirp
Carrier signal steps at a linear rate, “sweeping” across the spectrum
Direct Sequence
Generates a sin X / X signal
MUX
Multiplexing
DMUX
De-multiplexing
TDM
1) Time Division Multiplexing
2) Separates the transmission into TIME SLOTS
CDM
1) Code Division Multiplexing
2) Data is broken down into GROUPS of digital BITS
3) Groups (packets) can take many routes to get to their destination and be reassembled
FDM
1) Frequency Division Multiplexing
2) Signals are separated from each other/the carrier by an amount equal to the signal’s frequency
SAP
Separate Audio Program
Inverse Square Law
Signal falls 6 dB for every distance doubled, from the transmitter
Obstacles’ effects on waves
1) Reflection
2) Refraction
3) Diffraction
DCA-30 (antenna)
- 10 kHz - 2 GHz range
- Active
- Omnidirectional
- E field (far field)
Omnidirectional Wide Band (OWB) -60 (tuna can - antenna)
- 2-18 GHz range
- Passive
- Omnidirectional
- E field (far field)
VWA-30 (whip - antenna)
- VHF/UHF range; usable < 1 GHz
- Passive
- Omnidirectional
- E field (far field)
Active Loop Receiver (ALR) -30B (antenna)
- 9 kHz - 30 MHz range
- Active
- Bidirectional
- E/H field (far/near field)
Magnetic Field Coil (MFC) -30N (antenna)
- 30-300 MHz range
- Passive
- Bidirectional
- H field (near field)
Log Periodic Antenna (LPA) 30S
- 300 MHz - 1 GHz range
- Passive
- Unidirectional
- E field (far field)
Log Periodic Antenna (LPA) 60
- 1-18 GHz range
- Passive
- Unidirectional
- E field (far field)
Delta Configuration Transformer
1) No neutral wire; only ground
2) Phase to ground = 120 V
3) Phase to phase = 208 or 240 V
4-Wire Wye Configuration Transformer
1) Phase to phase = 208 V
2) Neutral to ground = 0 V
3) Phase to neutral = 120 V
4) Phase to ground = 120 V
3-Wire Wye Configuration Transformer
1) Phase to phase = 240 V
2) Neutral to ground = 0 V
3) Phase to neutral = 120 V
4) Phase to ground = 120 V
Branches on same phase
0 V
Branches on different phase
208 or 240 V
White wire
Neutral (CONUS)
Green or bare copper wire
Ground (CONUS)
Red, blue, black, or [sometimes] brown wire
Phase (CONUS)
4 steps in the analog to digital (AD) process
1) Filter
2) Sample
3) Quantize
4) Encode
OOK
On-off keying
PCM
Pulse Code Modulation
Nyquist Standard
Sampling frequency must be at least twice the highest frequency being sampled
If Nyquist Standard is not followed
Results in aliasing (false signal)
PAM
1) Pulse Amplitude Modulation
2) TIME change affects pulse AMPLITUDE
3) FREQUENCY change affects spectral line AMPLITUDE
PDM (or PWM)
1) Pulse Duration (or Width) Modulation
2) TIME change affects pulse WIDTH
3) FREQUENCY change affects D.O.
PPM
1) Pulse Position Modulation
2) TIME change affects pulse PERIOD
3) FREQUENCY change affects spectral line SPACING/PRF
PRF
1) Pulse Repetition Frequency
2) Inverse of pulse period (PP)
D.O.
1) Drop-out spacing/point
2) Inverse of pulse width (PW)
D.C.
1) Duty cycle
2) Inverse of spectral lines
3) PW / PP
FMCAB
Frequency Modulation (type) Content Amplitude Bandwidth
Pulse analysis
Measure from 50% amplitude/width
Links in digital communication
1) Synchronous or asynchronous
2) Synchronous implies that the transmit and receive clocks are locked together
FSK
1) Frequency Shift Keying
2) A form of data transmission in which the modulating wave shifts the output between 2 predetermined frequencies
PSK
1) Phase Shift Keying
2) A form of data transmission in which data causes the phase of the carrier to shift by a predefined amount
3) A constellation diagram is used to plot the phase changes
QAM
1) Quadrature Amplitude Modulation
2) Uses instantaneous amplitude and phase changes
3) QAM-16 = 4 bits, QAM-32 = 5 bits…, QAM-256 = 8 bits, etc.
AMDSB - IN
1) Time domain shows fc + fi orriented SBs
2) Frequency domain shows envelope:
a) Intelligence signal = 1 / fi
b) Carrier signal = 1 / fc
AMDSB - IF
1) Time domain shows fc + fi orriented SBs; centered at IF frequency
2) Frequency domain shows envelope:
a) Intelligence signal = 1 / fi
b) Carrier signal = 1 / fc (of IF)
AMDSB - Detected out
1) Time domain shows fi; carrier stripped away
2) Frequency domain shows sine wave of 1 / fi
Narrow band FM
< 15 kHz
Wide band FM
> 15 kHz
Carrier deviation
How far the carrier moves from its carrier position
Resolution Bandwidth (RBW) too large
Excess noise
Pulsing audio from speakers
Zero span not on
